Polynucleotide adsorption to negatively charged surfaces in divalent salt solutions
Polynucleotide adsorption to negatively charged surfaces in divalent salt solutions
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DOI：
10.1529/biophysj.105.070649
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发表时间：
2006-02-01
影响因子：
3.4
通讯作者：
Bedzyk, MJ
中科院分区：
文献类型：
--
作者：
Cheng, H;Zhang, K;Bedzyk, MJ
多核苷酸通过二价离子吸附到带负电荷的表面被广泛应用于生物系统的研究。本文通过一个自一致的平均场模型分析了吸附机理，该模型包括pH对表面电荷密度的影响以及二价离子与表面基团之间的相互作用。吸附是由二价金属离子沿多核苷酸缩合及其与表面基团反应的协同效应驱动的。虽然多核苷酸的存在提高了表观反应常数，但不同二价离子在理想条件下的反应常数之间的差异解释了为什么不是所有的二价阳离子都介导DNA在阴离子表面的吸附。计算的二价盐浓度和pH值对多核苷酸吸附的变化与原子力显微镜结果一致。在这里，我们使用长周期x射线驻波研究了锌cl2水溶液中汞化多尿酸在带负电荷的端羟基二氧化硅表面的吸附。这些现场x射线测量同时显示了沿表面法线方向的汞和锌分布剖面，与我们的模型吻合得很好。该模型还提供了聚电解质线电荷密度和单价盐对吸附的影响。
Polynucleotide adsorption to negatively charged surfaces via divalent ions is extensively used in the study of biological systems. We analyze here the adsorption mechanism via a self-consistent mean-field model that includes the pH effect on the surface-charge density and the interactions between divalent ions and surface groups. The adsorption is driven by the cooperative effect of divalent metal ion condensation along polynucleotides and their reaction with the surface groups. Although the apparent reaction constants are enhanced by the presence of polynucleotides, the difference between reaction constants of different divalent ions at the ideal condition explains why not all divalent cations mediate DNA adsorption onto anionic surfaces. Calculated divalent salt concentration and pH value variations on polynucleotide adsorption are consistent with atomic force microscope results. Here we use long-period x-ray standing waves to study the adsorption of mercurated-polyuridylic acid in a ZnCl2 aqueous solution onto a negatively charged hydroxyl-terminated silica surface. These in situ x-ray measurements, which simultaneously reveal the Hg and Zn distribution profiles along the surface normal direction, are in good agreement with our model. The model also provides the effects of polyelectrolyte line-charge density and monovalent salt on adsorption.